Observational study to estimate the changes in the efficacy of BCG with time since vaccination

The BCG vaccine’s protection against tuberculosis fades over time, but no one has precisely measured how fast—this study will track that decline in two age groups. Tuberculosis remains a serious infectious disease in the UK, particularly among vulnerable populations. The BCG vaccine is given to infants at high risk and was previously given to all schoolchildren until 2005. Public health officials need to know how long protection lasts to decide whether booster doses or revised vaccination schedules are necessary. Without this data, vaccination policies rely on assumptions rather than evidence. The researchers will analyse health records to compare BCG vaccination rates in people who developed tuberculosis and those who did not. One study covers children up to age 17 who could have been vaccinated in infancy. The other covers adults aged 23 to 37 who were eligible for the school-age programme. By comparing the two groups, the team can estimate how vaccine effectiveness changes over years. If successful, this work will give the UK Health Security Agency and the Joint Committee on Vaccination and Immunisation the evidence needed to update national vaccination policy. That could mean reintroducing routine BCG for certain age groups, targeting boosters, or confirming that current practice is adequate.